The Prime Minister's longest serving political adviser is to be questioned under caution by the police investigating the cash-for-honours affair.
Jonathan Powell, Number 10's chief of staff, will be interviewed later this month about e-mails and documents discovered in Downing Street offices that indicate Labour Party backers were offered honours in exchange for loans or donations.
The memos were said to discuss which Labour lenders might be placed on a list to be submitted to the House of Lords Appointments Commission.
Mr Powell, 50, will be the 15 person to be interviewed under caution. He was first interviewed, not under caution, by police before the recent memos were found.
The move comes amid growing criticism of Lord Goldsmith, the Attorney General, for refusing to stand down from decisions over possible criminal charges arising from the investigation. Yesterday, Harriet Harman, the Constitutional Affairs minister, said Lord Goldsmith will stand aside from any such decisions.
Ms Harman, when challenged about whether the Attorney General would consider moving aside from discussions about any prosecution because of his position as a Labour cabinet minister, insisted: "Well I'm sure the Attorney General will if it comes to it, and there is a consideration of a prosecution - which we haven't got to yet."
She added: "But I'm sure that the Attorney will say how he is going to go about it and he will want to be sure that people respect the office of attorney, that they respect the way that prosecutions are decided on independently and everything is out in the open."
The Attorney General's consent is required to proceed with prosecutions for certain offences, including corruption. Lord Goldsmith, 56, who was made a life peer in 1999 and appointed by Tony Blair in 2001, is usually consulted by the Crown Prosecution Service over high-profile and complex cases. He is a former donor to the party and a close political ally of Mr Blair.
Senior opposition politicians said the Attorney General should follow the lead of Ken Macdonald, the Director of Public Prosecutions, who announced he would play no part in the case because he is a former colleague of the Prime Minister's wife, Cherie. Ms Harman, a former solicitor general, told ITV1's Sunday Edition programme: "I know the man - I worked in the next door room for four years - and he regards public confidence as incredibly important and independence and transparency."
A spokesman for the Attorney General said: "There is a normal and proper procedure for dealing with prosecutions in high-profile and complex cases which is normal to follow. It is too early to speculate further at this time as the police have yet to hand a file of evidence to the CPS for formal consideration of charges."
Three people have already been arrested: Lord Levy, a friend and close ally of Mr Blair, Sir Christopher Evans, the biotech millionaire who lent Labour £1m, and Des Smith, a government education adviser.Reuse content